1. Industrial Field of the Invention
The present invention relates to an improvement of a fuel check valve which can be provided between a fuel filler port and a fuel tank. It is particularly useful as a check valve of liquid fuel to be attached to a fuel supply pipe of a liquid fuel tank for an automobile including a gasoline engine or a diesel engine.
2. Description of the Prior Art
In order to prevent fuel from unfavorably flowing back to a fuel filler port in response to an increase of pressure in a fuel tank when fuel is supplied to the tank in an automobile or the like or in such occasions, a check valve has conventionally been provided in a flow passage. The valve is operated in such a manner as to be opened while the fuel is flowing in the normal direction at the time of fuel supply, and to be closed when the fuel splashes back and flows in the reverse direction. One example of such check valves is disclosed in the U.S. Pat. No. 4,128,111. This check valve is constituted of a valve body, a valve disc, a pivot pin and so on, and the number of such component parts is thus large. Besides, after the pivot pin is assembled with other members, it is necessary to crush both tips of the pivot pin so as to prevent the pin from coming off.
The inventors of the present application have tried to achieve facilitation of the assembly operation and reduction of the number of component parts of such a reverse flow preventing device for a fuel tank, and investigated the structure with which the valve disc will not come off easily and the assembled unit will not be detached from a pipe accidentally. As a result, the inventors could suggest a device of this type previously as U.S. application Ser. No. 758,891.
In the case where a reverse flow preventing device for a fuel tank comprises a single valve plate as the above-mentioned examples do, it must be installed at a predetermined location in a restricted direction to make it function normally. Moreover, there is a risk that fuel can not be supplied if the valve plate is stuck in the closed condition due to any adhesive substances such as tar and impurities of fuel depositing on bearing portions. Furthermore, the fuel flow within a fuel supply pipe is a turbulence at the time of fuel supply, and this is one of the causes of deterioration in fuel supply efficiency. Fuel should preferably be introduced into a tank as a laminar flow. One of the examples in which these factors are improved to some extent is disclosed in U.S. Pat. No. 4,774,981. In this example, however, the valve plate is divided into two sections, and therefore, it is still necessary to take the installation direction into account.
For this reason, the inventors developed and suggested in U.S. application Ser. No. 720,597 a reverse flow preventing device for a fuel tank, which is characterized in that it comprises a valve body whose annular inside space is divided equally into more than three sectorial sections on the division lines of which a pivot member is provided, and valve plates which have the shape corresponding to these sectorial sections and swing about the pivot member which serves as bearings, and that swinging restriction means are provided on the bearings of the pivot member so that swinging movements of the valve plates will be restricted to a range of 90.degree. or less and to a single direction.
This makes it possible 1 to eliminate the directional restriction in the installation of the device, 2 to decrease the risk at the time of malfunction of the valve plates, and 3 to provide the device with a flow straightening function as an additional function.
However, there are various kinds of fuels, and some of them, as gross gasoline, contain tar in large quantities. If ordinary shafts and bearings are used for such fuel, it is feared that tar will adhere to the valve plates to intervene their operations. The inventors further investigated the valve plates, developed the structure with which to prevent the malfunction of valve plates due to tar and impurities adhering to them and also to reduce the assembly labor, and suggested it in the above-mentioned U.S. application Ser. No. 720,597.
In this structure, the valve operating portion comprises a plurality of valve plates so that some of the valve plates will always be immersed in fuel and function to straighten the flow even if the valve plates are provided at a different angle. As a result, there will be no malfunction of the valve plates due to impurities adhering to them, and the assembly labor will be lessened.
With such a structure, however, if a bellows is provided in the vicinity of the check valve, it is feared that turbulence of the fuel flow or splashing of the fuel in the bellows makes the operation of the valve unstable.
It is therefore an object of the present invention to provide a structure which can prevent unstable operation of a check valve even if a bellows is provided near the check valve.